Suggestion: object const'ness

[Tom]

Hasan Aljudy escribió:
> Tom wrote:
>> Derek Parnell escribió:
>>
>>> .
>>>
>>>>
>>>> If you see a signature like this:
>>>>
>>>> void doSomething(in SomeObj obj1, inout SomeObj obj2);
>>>>
>>>> You'll instantly expect that function "doSomething" doesn't modify obj1
>>>
>>>
>>> But it doesn't modify 'obj1'. Remembering that 'obj1' is the 
>>> reference to the object and not the object itself.
>>
>>
>> If you read just below you'll notice I was referring to obj1 as the 
>> object and not as it's reference.
>> |
>> V
>>
>>>>    and do possibly modify obj2 (the object and not it's reference). 
>>>> Why would you want (in the most of the cases) to make "in" the 
>>>> reference itself?
>>>
>>>
>>> Don't know. Simplier I guess.
>>
>>
>> Exactly, no one knows why, it's simply useless. At present, in D is 
>> perfectly pointless (merely informative) to use 'in' with reference 
>> parameters, at least for the 99% of the cases.
>>
>>>> Currently D 'in Obj p' "behaves as" the rarely-used 'Obj *const p' 
>>>> and not as the widely and common 'const Obj *p' of C++ ("behave as" 
>>>> because I use pointers instead of references to illustrate the 
>>>> underlying behavior and C++ references are always const).
>>>>
>>>> Const is another level of protection against unintended behavior 
>>>> (i.e. bugs). In C++, const *can* be circumvented but one has to be 
>>>> horribly explicit to do that. No way you would unintentionally do that.
>>>
>>>
>>> So everyone repeat after me ... D is not C++, D is not C++, D is not 
>>> C++, ...  ;-)
>>
>>
>> I know that Derek. Just that *many* of the users that come to D, don't 
>> know if you realize it, comes from the C++ world. It's understandable, 
>> we like the features of C++ but hate the syntax (and other stuff) and 
>> we see D as a better C++. It's perfectly natural to try to achieve the 
>> same things in D that we've achieved in C++. Don't be afraid, I'd hate 
>> to see D become another C++ (and that's not gonna happen for sure).
>>
>> For C++ users, 'in' parameters (for references) are 'const Obj &o', 
>> inout/out parameters are 'Obj &o'. When you see that on a signature 
>> you can be "sure" (there's always some reasonable trust in the middle) 
>> the function will not modify the object (you don't care about the 
>> object reference). In D in/out/inout are just a disappointment (for 
>> C++ users). I've dreamed to see that keywords used with the same 
>> meaning as what I've mentioned above.
>>
>>> --Derek Parnell
>>> Melbourne, Australia
> 
> "D is not C++" implies the following:
> Don't try to achieve things the same way as in C++!!
> 
> It's not just the syntax that's different, it's a lot of features too.
> For example: objects are always by reference, never by value.
> This make for a huge difference; it results in a completely different 
> behaviour in many situations. (for the better).
> 
> I would advice you to try Java for a while, maybe it can help you get 
> rid of useless C++ idioms. :)

I work with JAVA as well. I like it as a language but I hate its VM, its 
gigantic JDK and its slowness. Native compiled Java would be great if 
you ask. Anyway I think I get your point.
Just a few questions, is in/out/inout useful for you in any way? 
Wouldn't it be more honest to remove in/out/inout and replace it for 
some kind of 'byref' attribute?

Regards,
--
Tom;